Preparation of rubberlike copolymer of 1, 3-butadiene and styrene which contains amine activator



Patented July 19, 1949 2,476,822 3 PREPARATION or RUBBERLIKE COPOLYJ MER F .1,3-BUTADI WHICH CONTAINS AMHNE ENE AND STYREN E AC TIVATOR 7 Alvin D. Miller, Cuyahoga Falls, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Qhio, aroorporation of Ohio Serial No. 623,860

No Drawing. Application October 22, 1945.

2 Claims. (Cl. 5260-85- 1) invention relates to a synthetic rubber to he used for wire insulation, :as forinsulating cables, etc. More 'particularlmit relates to such insulation prepared from .a rubber-like copolymer of 1,3-butadiene and styrene which contains as an activator :of vulcanization acceleration an alkyl pr imary amine :salt .of a soap-forming fatty acid. The invention includes the vulcanization of such a rubber as insulation around a wire.

It is recognized that "for wire insulation alumcoagulated rubber like flcopolymers iof 1,3-butadiene and styrene i sudh as the rubber known as GR-S) are superior to such copolymers coagulated by other reagents because of their low ash, etc. However, the continuous :cure used by most wire manufacturers linoludingmanufacturers of cable) requires aflfa'ster curing compound than the usual GR B mixes. The first attempts to accelerate "the cure by adding an amine to the latex-were unsuccessful because the amine forms a salt with the soap used as a dispersing aeent in the copolymer latex; -andsuch salt formation, by removing soap from the reaction mixture, caused prefiocculation or 'preooagulation.

It has been found that the amine salt of a fatty acid has the same activating -'eifect as the amine itself. According to the present invention, the amine salt "is used as the activator. The amine may be added as a salt, -or it "may be added to -a latexwhich contains su-fficient'excess soap to produce a salt without precoagulation. 7

The amine used as an aetiva toris a primary alkylmonoamine --conta-i ning, for example, about eight up to "twenty or more carbon atoms, such as octylamine, 'dodecy-lamine, *stearylamine, etc.-

A commercial "mixture of such amines sold by Armour-and Company, of Chicago, as AM118.5B is satisfactory and was used in the operations to which the following examples refer. The salt is produced by reacting the :am-ir-re with an equivalent amount of a soap-forming :fatty :acid, such as stearic acid, .oleic acid, etc. The salt formed is referred to herein as a primary alkylmonoamine :salt of soap-forming zf-altty acid containing eight to about twenty carbon atoms in the alkl/l .group.'

The following examples are illustrative .of .the invention:

Example 1 In this example the copolymer was prepared l according to the following formula:

Parts per 100 parts monomer Water 180 1,3-Butadiene 72 Styrene 28 Catalyst (potassium persulfate) 0.3 Modifier (mixed high-er aim imercaptans") 0.46 Soap chips 4.75 Stearic acid Q 0.-6

The amine soap was added after Lcopolymerizatron and removal .of unreacted L'3-lbutadiene and styrene; i. e., afterjlthe .iisual stripp n operation. Th rteen pounds of the commercial AM118.5B amine (0.20 part per 100 parts of the dry rubber) were melted and added with agitation to 20 gallons of 9.1 per cent soap solution .at 70 C. After about 5 :minutes, during which the mixture became more viscous, the solution was diluted to 40 gallons having a soap content of 4.55 per cent. This solution contains no more than a slight excess of soap over that required for formation of the amine salt. The emulsion prepared in this way was added to the latex at a. temperature of C. after stripping. The anti-oxidant which was of a usual type was added in the usual manner at the beginning of the st "pping operation.

For coagulation a 2 per cen-t solution of employed. 'The amount usedwas equivalent tori pounds col AlzCSOth per pounds ofGR-rS. i'lihe GR-S .coagulum was dried at 230 around 14 or :15 hours, and the reaction temperature was 123 F. The mioduct had an ,ash :of 0.50 per cent, and on curing .at 292 tor the minutes indicated in the following table, test samples were found to have the following physical properties: r

IE. The .copo'lymer reaction took star Crude stock: Mooney (L4) I -42 Compound'ed stock: Mooney (LD L '53 Cure temperature E 292 292 Elongation: i

use .760 i525 625 555 too .295 535 835 l, 035 1;2502 11,350

The improved rubber is designed for cable and with vulcanizing ingredients as any other GR-S rubber; and plasticizers, etc., may be added as is usual in the preparation of wire and cable insulation. The coatings will preferably be applied by extrusion in the usual manner, and due to the presence of the amine'salt the vulcanization will be more rapid than with usual GR-S vulcanizations. The cure may be carried out at 292 F. or at any other desired temperature.

Example [2 Another example was prepared according to the following copolymerization formula:

Parts per 100 parts monomer Water 180 Catalyst 0.3 Soap 5.0 Styrene 25.0 Modifier 0.7 1,3-Butadiene 75.0 Amine (Al/1118.5B) 0.2

agulated in the usual by adding 4 parts of From the standpoint of production the procedure of Example 3 or of Example 1 appears preferable. The procedure of Example 1 has the advantage that it is possible to select a batch of preferred Mooney (between about 39 and 45, known as GR-S type before adding the amine.

The dispersions of Examples 2 and 3 were coway with aluminum sulfate aluminum sulfate per 100 parts of the monomer. It cures rapidly and is in every way satisfactory for wire insulation.

Tests using a relatively pure amine, such as dodecylamine, instead of the commercial amine of the above examples gave satisfactory results.

The invention is not limited to the above de- 7 tails but is defined in the appended claims. The

Catalyst 0.3 Soap 5.0 Styrene i 25.0 Modifier 0.1 1,3-Butadiene 75.0 Amine (AM118.5B)-; 0.2

The molten amine was poured into a concentrated soapsolution at 155 F. under agitation, and afterg flz hours agitation the solution was brought to proper concentration by addition of the balance of the :water'. The reaction time for 1200 pounds-of -n'ionomer wa'sT15 /2 hours, and the reaction temperaturewvas 122 F. The Mooney (MLr) of the'crude. was 51; and of the compounded rubber, 53. +1

Test samples of Examples 2 and 3 cured at 292 F. for the number of minutes indicated in the following table had the following properties:

' 55%??? Control Example 2 Example 3 Mmttes- 25 750 625 635 Elongation 50 625 520 550 90- -555 510 500 25 395 625 740 300% M0dll1l1S 50 535 1, 050 1, 175 9c 1, 250 1, 215 1, 475 4 25 850 1, 300 1, 575 500% Modulus- 50 1, 800 2, 17 5 2, 425 90 2, 525 2, 650 3, 025 25 1, 340 1, 050 2, 100 Tensile 50 2, 435 2, 300 2, 900 a so 3, 000 2, 750 3, 025

amine may be added before reaction with fatty acids or as a salt. If sufficient soap is employed, the amine may be added during coagulation or after. If carbon black or other pigment is compounded with the latex, the amine may be reacted with soap in the pigment dispersion and may be added to the latex with the pigment.

What I claim is:

1. The method of producing rubber-like coagulum of 1,3-butadiene and styrene, which coagulum contains uniformly distributed therein a salt of a primary alkyl monoamine for activation of the vulcanization of the copolymer, the alkyl group containing eight to twenty'carbon atoms, the amine being otherwise unsubstituted, which comprises coagulating with aluminum sulfate the dispersion of copolymer which results from emulsion copolymerization of the 1,3-butadiene and styrene and contains suflicient soap to maintain a, dispersion of the coagulum and in addition contains a small amount of the primary monoamine salt of soap-forming fatty acid whereby coagulum of the copolymer is obtained which contains uniformly distributed therein suflicient of said amine salt to serve as an accelerator of vulcanization on subsequent vulcanization of the copolymer.

2. The method of producing rubber-like coagulum from soap-dispersed emulsion resulting from emulsion copolymerization of 1,3-butadiene and styrene, which comprises adding to the emulsion a soap-dispersed emulsion containing primary alkyl monoamine salt of soap-forming fatty acid sufficient to serve as an activator of the vulcanization of the copolymer, the alkyl group containing eight to twenty carbon atoms, the amine being otherwise unsubstituted, and then coagulating the resulting emulsion with aluminum sulfate to obtain coagulum of the copolymer in which said amine salt is uniformly distributed.

ALVIN D. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Sarbach 1 Feb. 26, 1946 

